As renewable capacity continues to expand and the need for grid stability increases, batteries are taking on a larger role.

Recent data confirms this trend. As reported in June 2024 by the online news source Power Grid International, more utilities are using batteries to help them manage power demand and maintain grid stability.

The article draws on data released recently by the U.S. Energy Information Administration (EIA). In June, the EIA published an early release of data from its EIA-860, Annual Electric Generator Report. According to the data, U.S. utilities reported using 575 batteries at the end of 2023. The collective capacity of these storage units reached 15,814 megawatts (MW). EIA also expects U.S. battery capacity to more than triple, with nearly 40,000 MW of additional capacity added by the end of 2028.

Utilities incorporate batteries for many different reasons. Batteries can help with storage of excess solar and wind generation, and various functionalities that support transmission, also known as ancillary services. These include frequency regulation, load management, system peak shaving and other services.

According to the data, utilities are using batteries primarily for arbitrage, with 10,486 MW of battery capacity reported for that purpose. In arbitrage, utilities take advantage of price fluctuations to reduce risk and increase profits. They use batteries to store power when the prices are low, then discharge and sell the power when prices are higher.

As a case in point of the growing popularity of utility scale batteries, an Arizona utility recently announced two new grid-charged battery storage systems. In June, Salt River Project (SRP), the primary power provider in the Phoenix area, announced a partnership with battery owner and operator, Plus Power, to install and run two new battery systems in the utility’s service area.

The 250-MW Sierra Estrella Energy Storage facility, located in Avondale, Ariz., will store enough energy to power more than 56,000 homes for a four-hour period. It is SRP’s largest grid-tied battery, and according to the utility, is now the largest standalone battery in the state.

The 90-MW Superstition Energy Storage facility, located in Gilbert, Ariz., will store enough energy to serve more than 20,000 homes for a four-hour period.